The weather is important to everyone. Will it rain today, will I need a jacket? But what is space weather? Is there really "weather" in outer space? Isn't space almost a perfect vacuum? UCLA has been studying this for some time and recently completed a study that sheds important light on space weather. Solar storms — powerful eruptions of solar material and magnetic fields into interplanetary space — can cause what is known as "space weather" near Earth, resulting in hazards that range from interference with communications systems and GPS errors to extensive power blackouts and the complete failure of critical satellites.

Some of the energy emitted by the sun during solar storms is temporarily stored in Earth's stretched and compressed magnetic field. Eventually, that solar energy is explosively released, powering Earth's radiation belts and lighting up the polar skies with brilliant auroras. And while it is possible to observe solar storms from afar with cameras, the invisible process that unleashes the stored magnetic energy near Earth had defied observation for decades.

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In the Sept. 27 issue of the journal Science, researchers from the UCLA College of Letters and Science, the Austrian Space Research Institute (IWF Graz) and the Japan Aerospace Exploration Agency (JAXA) report that they finally have measured the release of this magnetic energy close up using an unprecedented alignment of six Earth-orbiting spacecraft and NASA's first dual lunar orbiter mission, ARTEMIS.

Space weather begins to develop inside Earth's magnetosphere, the giant magnetic bubble that shields the planet from the supersonic flow of magnetized gas emitted by the sun. During solar storms, some solar energy enters the magnetosphere, stretching the bubble out into a long, teardrop-shaped tail that extends more than a million miles into space.

The stored magnetic energy is then released by a process called "magnetic reconnection." This event can be detected only when fast flows of energized particles pass by a spacecraft positioned at exactly the right place at the right time.

Luckily, this happened in 2008, when NASA's five Earth-orbiting THEMIS satellites discovered that magnetic reconnection was the trigger for near-Earth substorms, the fundamental building blocks of space weather. However, there was still a piece of the space weather puzzle missing: There did not appear to be enough energy in the reconnection flows to account for the total amount of energy released for typical substorms.

In 2011, in an attempt to survey a wider area of the Earth's magnetosphere, the THEMIS team repositioned two of its five spacecraft into lunar orbits, creating a new mission dubbed ARTEMIS after the Greek goddess of the hunt and the moon. From afar, these two spacecraft provided a unique global perspective of energy storage and release near Earth.

Graphic shows process of magnetic reconnection, which powers the phenomena known as space weather. Credit UCLA.